Power shovels are in a category of excavation equipment used to remove large amounts of overburden and ore during a mining operation. One type of power shovel is known as a rope shovel. Another type of power shovel is known as a dredge, and dredges are typically used to remove material from below a waterline. A rope shovel includes a boom, a dipper handle pivotally connected to a mid-point of the boom, and a bucket (also known as a dipper) pivotally connected at one end of the dipper handle. A cable extends over a sheave at a distal end of the boom and terminates at the end of the dipper handle supporting the dipper. The cable is reeled in or spooled out by electric, hydraulic, and/or mechanical motors to selectively raise and lower the dipper.
In most rope shovels or dredges, the dipper includes a door that is selectively swung open to dump material from the dipper into a waiting haul vehicle. The door is pivotally connected at one edge to a dipper body, and mechanically latched at an opposing edge. A cable extends from an operator cabin over a boom-mounted sheave to the dipper latch. In this configuration, an operator can actuate the latch from inside a cabin of the shovel by tensioning the cable. When the dipper is held vertically, tensioning the cable causes the latch to release the door and the door falls open under the force of gravity. When the dipper is held horizontally, the door swings shut against the dipper body under the force of gravity, and the latch is biased to re-engage and hold the door in the closed position.
Although adequate for some applications, use of the cable to manually cause actuation of the dipper latch can be problematic. In particular, typical latches and associated cable linkages are under tremendous strain and cycle continuously. As a result, these components suffer high-cycle fatigue and must be serviced frequently to ensure that the latch operates effectively when manipulated by the operator via the cable. This frequent servicing results in machine downtime and lost productivity. Accordingly, an alternative source of control at the dipper latch is desired.
One attempt to improve durability of the dipper is disclosed in U.S. Pat. No. 8,136,272 that issued to Hren et al. on Mar. 20, 2012 (“the '272 patent”). Specifically, the '272 patent discloses a dipper door latch having a hydraulic cylinder that is remotely activated to selectively lock and unlock movement of the door. The cylinder is a double-acting cylinder having opposing chambers connected to each other by way of a closed loop. A solenoid operated valve, powered by a battery pack located at the dipper, controls fluid flow between the chambers in response to a remotely-transmitted signal from the operator. An accumulator is connected to the loop to accommodate volume differences between the chambers.
Although the dipper door latch of the '272 patent may have improved durability because it no longer requires mechanical connection to the cab of the power shovel, it may still be problematic. In particular, the double-acting nature of the cylinder increases a complexity of the latch and the potential for malfunction. Further the location and configuration of the latch and hydraulic cylinder could result in elevated wear.
The exemplary embodiments of the present disclosure solve one or more of the problems set forth above.